We present new flux-calibrated narrow-band images of the circumnuclear region in M81=NGC 3031 in the light of [OIII] lambda5007, [OI] lambda6300, Hα+[NII] lambdalambda6548, 84 and [SII] lambdalambda6717+31 emission lines. The Hα+[NII] and [OIII] images as well as [OI] and [SII] ones reveal the existence of an extended emission-line structure around the nucleus of M81. The Hα+[NII] lambdalambda6548, 84 extends to ~8 arcsec west and ~13 arcsec east of the nucleus at the 5sigma noise level of the image. The estimation of the filling factor, between 5x10^-4 and 3x10^-3, was made based on the emissivity in the [OIII] and Hα regions, respectively. An increase of the [OIII]/Hα ratio was detected, growing more prominent farther from the nucleus. This is caused by increasing [OIII] lambda5007 emission rather than decreasing Hα+[NII] emission. The [OIII]/Hβ against [OI]/Hα diagnostic diagram for the circumnuclear emission-line region (CELR) around the nucleus implies that part of the ionization, particularly in the innermost nuclear regions, could be accounted for by an AGN-like power-law ionization spectrum. Another part of the ionization, particularly in outer regions of the CELR, is caused by diffuse thermal X-ray continuum.